Method to evaluate patients for thoracic outlet syndrome

ABSTRACT

Improvements in magnetic resonance imaging methods to obtain three-dimensional models and diagnoses of Thoracic Outlet Syndrome are described.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit of priority under 35 USC 119.(3) to U.S. Ser. No. 60/840,887 filed 28 Aug. 2006. The content of this document is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to methods of evaluating and diagnosing Thoracic Outlet Syndrome (TOS) using magnetic resonance imaging and magnetic resonance angiography.

BACKGROUND ART

The brachial plexus is a large cluster of nerves that passes from the spinal cord through the neck and the upper chest to the shoulder and arm. To reach the arm, the brachial plexus must pass through at least three anatomic tunnels. The main blood supply to and from the arm is provided by the subclavian artery and the subclavian vein, respectively. These major blood vessels pass through the same anatomic tunnels as the brachial plexus. Thoracic Outlet Syndrome (TOS) is a complex of signs and symptoms that results from narrowing of these tunnels and compression of one or more of these vital structures. TOS can be divided into three primary types:

-   -   Neurogenic Thoracic Outlet Syndrome: Neurogenic TOS is a         compressive and entrapment neuropathy in which one or more of         these tunnels becomes narrow, creating mechanical compression on         the brachial plexus and/or altering its blood supply. This         compression and altered blood flow result in pain, abnormal         sensation, weakness, and eventual loss of muscle function in the         affected areas.     -   Arterial Thoracic Outlet Syndrome: Arterial TOS results from         mechanical compression of the subclavian or axillary artery,         which causes arterial stenosis, post-stenotic aneurysm         formation, and intramural thrombus formation. These changes         result in decreased blood flow to the arm and/or embolism of         thrombus to distal vessels, with pain, weakness, coldness and         loss of pulse in the affected arm.     -   Venous Thoracic Outlet Syndrome: Venous TOS results from         mechanical compression of the subclavian or axillary vein, which         causes occlusive or non-occlusive thrombosis of the vein, damage         to the lining of the vein, and eventual stricture formation that         persists despite resolution of the extrinsic mechanical         compression. These changes result in swelling, cyanosis, pain         and altered function of the affected arm.

The causative mechanisms for all three types of primary TOS are nearly identical, and compression of one vital structure is often accompanied by compression of the other vital structures in varying degrees. Therefore, each primary type of TOS described above frequently includes a component of one or both of the other two types of TOS.

Thoracic Outlet Syndrome occurs when two conditions are met:

-   -   The patient has anatomic predispositions or anomalies. These can         include abnormal muscles or fibrous bands, exaggeration or         distortion of the usual shapes of the chest and shoulder girdle         bony structures, anomalous courses of the nerves that make up         the brachial plexus, or anomalous arteries or veins that pass         through the thoracic outlet.     -   The patient has a superimposed traumatic event or repetitive         overuse syndrome that:         -   Alters the soft tissues or bony structures that make up the             anatomic tunnels, or         -   That causes direct injury to the brachial plexus, arteries,             veins or soft tissues and bony structures that make up the             anatomic tunnels, or         -   That alters the posture and position of the neck and             shoulder girdle, leading to narrowing of the anatomic             tunnels through which the brachial plexus, arteries and             veins pass.

Neurogenic TOS is a compressive and entrapment neuropathy that has been clinically recognized for over one hundred years. Physicians frequently find these patients' cases complex and challenging. Patients often have a slowly-evolving course, experiencing symptoms intermittently early in the course of the disease and often only being symptomatic with the arms and neck in certain positions. As the disease progresses, the patients experience symptoms continuously, regardless of the position of their arms and neck. Patients often experience sensory changes early in the course of the disease, followed by vague muscle aching as the disease progresses. Eventually, patients experience muscle weakness, which in the late stages becomes evident as muscle atrophy and wasting, if the correct diagnosis is not made and definitive treatment is not undertaken. Unfortunately, when the disease progresses to this extent, muscle weakness and atrophy are unlikely to improve, even with definitive treatment.

Arterial TOS is frequently associated with an anomalous extra rib in the lower cervical spine, and was the first clinical form of TOS to be recognized, beginning with a case described in England in 1821, followed by a surgically proven case in 1861. It often has a dramatic clinical presentation due to either decreased blood flow to the affected arm or to the sudden development of blood clots embolizing to the distal vessels of the arm, causing gangrene. In this setting, the diagnosis is readily made. However, early diagnosis is critical to prevent the occurrence of these potentially serious complications.

Venous TOS frequently occurs in patients with an occupation requiring repetitive and/or strenuous use of their upper extremities, and is known by several other names, including effort thrombosis and Paget-Schroetter syndrome. It often has a dramatic clinical presentation due to swelling of the affected arm, decreased blood flow or loss of function. In addition, these patients are at risk of pulmonary embolism and pulmonary hypertension, either of which may be fatal. In this setting, the diagnosis is readily made. However, early diagnosis is critical to prevent the occurrence of potentially serious thromboembolic events, and to prevent permanent damage to the compressed vein, which predisposes the patient to repeated episodes of thrombosis formation and symptoms even after the mechanical compression of the vein has been treated.

Clinical, electrophysiologic and imaging tests have been developed over the past century, but none have been widely accepted as a gold standard for the diagnosis of TOS. Clinical tests utilize various positions of the patient's neck and arms while the pulse is palpated at the wrist. These tests have been shown to have a high number of false positive and false negative results. Electrophysiological tests are used to rule out the presence of other compressive and entrapment neuropathies of the upper extremity, but can not confirm or rule out the diagnosis of TOS. Imaging tests have been used to evaluate the anatomy and pathology in patients with TOS. These tests have changed as the technology has evolved to allow more refined evaluation of anatomy and pathology in patients with TOS.

Since the 1960's, contrast angiography or venography has been performed to evaluate the arteries or veins of the arms, respectively, with the patient's arms placed in various provocative positions. This method duplicates the clinical tests in which the patient's pulse is palpated as their arms are moved into symptomatic positions. Angiography and venography are limited to evaluation of the compressed arteries and veins, but do not evaluate the abnormal anatomic tunnels that are causing this compression. Since the 1980's, CT scanning has been performed to evaluate the bony structures that border the thoracic outlet, or the arteries and veins of the arms, with the patient's arms placed in various provocative positions. CT scanning can also be performed with the patient's arms by their sides, allowing evaluation of the changes in the bony anatomic tunnels that occur with arm motion, and the resulting effects on the accompanying arteries or veins. CT scanning is limited in its evaluation of soft tissues, with inadequate differentiation of muscles and nerves in the thoracic outlet. Since the early 1990s, MRI scanning has been performed for the evaluation of soft tissue structures in the thoracic outlet, including the nerves of the brachial plexus, the arteries and veins of the arm, or the muscles that border the anatomic tunnels through which these vital structures pass to reach the arm. Like CT scanning, MRI scanning can be performed with the patient's arms placed in various provocative positions.

Each of these imaging tests has focused on one component of TOS, evaluating the bony structures, soft tissues, arteries, veins, or nerves. To date, there has been no single process that evaluates comprehensively the nerves, arteries and veins that pass through the thoracic outlet, the muscles and bony structures that form the anatomic tunnels of the thoracic outlet, the changes in the thoracic outlet that occur on arm movement, and the resulting effects of these changes on the brachial plexus, arteries and veins as they pass through these tunnels. The invention technique accomplishes these goals.

DISCLOSURE OF THE INVENTION

The invention provides a comprehensive process that permits accurate evaluation of patients for the presence or absence of Thoracic Outlet Syndrome (TOS). The invention employs magnetic resonance imaging techniques, magnetic resonance angiography and, optionally, magnetic resonance venography. Images are obtained as the basis for 3-dimensional models which are reviewed in addition to the original images by a radiologist according to a checklist of items with respect to each model and image.

Thus, in one aspect, the invention is directed to

A method to evaluate a human subject for the presence or absence of thoracic outlet syndrome (TOS) which method comprises:

a) obtaining a first set of magnetic resonance imaging (MRI) slices in each of three planes, in the absence of contrast agent,

with the subject in a supine position with both arms in a neutral position by the side of the body,

using a surface coil placed to cover the upper chest and neck, and the supraclavicular fossa region on the affected side(s),

wherein a gradient echo T1, spin-echo T1, or fast spin echo T2-weighted sequence comprises sagittal slices that cover the scalene triangle, costoclavicular space, and retropectoralis space on the affected side(s); and

wherein a gradient echo T1, spin-echo T1, or fast spin echo T2-weighted sequence comprises axial slices that cover the mid and lower cervical spine and lower neck, and the brachial plexus, supraclavicular space, superior mediastinum and lung apex on the affected side(s); and

wherein a Short Tau Inversion Recovery (STIR) sequence comprises coronal slices that cover the volume of the brachial plexus on the affected side(s);

b) obtaining a second set of MRI slices in one or more planes,

with the subject in a supine position with both arms placed in abduction and external rotation,

using a surface coil placed to cover the upper chest and neck, and the supraclavicular fossa region on the affected side(s),

wherein the sequence that comprises the sagittal slices are obtained as in subparagraph a), in the absence of contrast agent, followed by

an optional sequence that comprises the axial slices, obtained as in subparagraph a), in the absence of contrast agent, followed by

intravenously administering a contrast agent, and

obtaining a contrast-enhanced magnetic resonance angiogram (MRA) during the arterial enhancement phase following said administering which comprises coronal slices prescribed to cover the subclavian and axillary arteries on the affected side(s); after which,

optionally obtaining a magnetic resonance venogram (MRV) performed during the arteriovenous equilibrium or venous enhancement phase following said administering which comprises coronal slices prescribed to cover the subclavian, axillary and brachiocephalic veins on the affected side(s);

c) composing the slices from the STIR sequence into a composite volume, and editing the composite volume to create a three-dimensional model of the brachial plexus on the affected side(s);

d) composing the slices from the MRA into a composite volume, and editing the composite volume to create a three-dimensional model of the arteries on the affected side(s); and

e) composing the slices from the MRV, if performed, into a composite volume, and editing the composite volume to create a three-dimensional model of the veins on the affected side(s); and

f) evaluating the first and second sets of MRI slices of a) and b) and the three-dimensional models of c) and d) and optionally e) according to a checklist,

whereby the presence or absence of TOS in the subject is evaluated.

The evaluation data a may also be stored on electronic media for future reference. Accordingly, in another aspect, the invention is directed to an electronic recording medium comprising evaluation data obtained according to the checklist described herein.

MODES OF CARRYING OUT THE INVENTION

In general, the method of the invention involves obtaining a series of images, manipulating these images, and drawing conclusions from them according to a checklist of locations and evaluations. The radiologist will typically view and evaluate between 700 and 1,000 images displayed on a work station, for a patient who has both sides examined. A detailed description of the images to be obtained is as follows. While gadolinium is used as the contrast agent below, alternative similarly responding contrast agents, including but not limited to paraCEST agents may be used.

The patient is placed in supine position in the MRI scanner, with both arms in neutral position, by the side of the body. A neurovascular coil or similar coil that covers the upper chest, neck and supraclavicular fossa region on each side is used. The following sequences are then performed:

-   -   3D localizer sequence, using gradient recalled technique.     -   Coronal STIR (Short Tau Inversion Recovery) sequence, prescribed         to cover the volume of the brachial plexus on the affected         side(s).     -   Sagittal gradient echo T1, spin-echo T1 or fast spin echo         T2-weighted sequence, prescribed to cover the scalene triangle,         costoclavicular space and retropectoralis space on the affected         side(s).     -   Axial gradient echo T1, spin-echo T1 or fast spin echo         T2-weighted sequence, prescribed to cover the mid and lower         cervical spine and lower neck, and the brachial plexus,         supraclavicular space, superior mediastinum and lung apex on the         affected side(s).

The patient is then removed from the scanner, placed back in the scanner with both arms in abduction and external rotation, and a coil is placed to cover the patient's upper chest, neck and supraclavicular fossa region on each side. An intravenous line is placed in the patient's antecubital or hand vein at this time, if one has not already been placed earlier. This intravenous line is connected to a standard MRI power injector. The injector is pre-loaded with one syringe of normal saline (optional), and one syringe containing gadolinium contrast material, or a mixture of gadolinium contrast material and normal saline. The following sequences are then performed:

-   -   3D localizer sequence, using gradient recalled technique.     -   Sagittal gradient echo T1, spin echo T1 or fast spin echo         T2-weighted sequence, prescribed to cover the scalene triangle,         costoclavicular space and retropectoralis space on the affected         side(s).     -   Axial gradient echo T1, spin echo T1 or fast spin echo         T2-weighted sequence, prescribed to cover the mid and lower         cervical spine and lower neck, and the brachial plexus,         supraclavicular space, superior mediastinum and lung apex on the         affected side(s).     -   Time of flight angiogram, oriented in the coronal plane,         prescribed to cover the subclavian, axillary and brachial artery         on the affected side(s), performed during the arterial         enhancement phase following injection of gadolinium contrast         material via the previously placed intravenous line.     -   Time of flight venogram, oriented in the coronal plane,         prescribed to cover the subclavian, axillary and brachial artery         and vein on the affected side(s), performed during the venous or         equilibrium enhancement phase following injection of gadolinium         contrast material via the previously placed intravenous line         (this sequence is optional).

After the above images have been produced, the following reconstructions and reformations are performed on selected images:

-   -   The images from the STIR sequence are assembled into a volume         and edited to create a 3-dimensional model of the brachial         plexus on the affected side(s). This model can be displayed in         any plane.     -   The images from the time of flight angiogram are assembled into         a volume and edited to create a 3-dimensional model of the         arteries on the affected side(s). This model can be displayed in         any plane.     -   The images from the optional time of flight venogram are         assembled into a volume and edited to create a 3-dimensional         model of the veins on the affected side(s). This model can be         displayed in any plane.

In patients with prior surgery for decompression of the thoracic outlet, the following optional sequences can be performed:

-   -   Axial gradient echo or fast spin echo T1 weighted sequence,         prescribed to cover the surgical bed on the affected side(s).     -   Sagittal gradient echo or fast spin echo T1 weighted sequence,         prescribed to cover the surgical bed on the affected side(s).

This process may be described in further detail as follows:

The patient is placed in supine position in the MRI scanner, with both arms in neutral position, by the side of the body. A neurovascular coil or similar coil that covers the upper chest, neck and supraclavicular fossa region on each side is used. The following sequences are then performed:

-   -   1. 3D localizer sequence, using gradient recalled technique.     -   2. Oblique coronal STIR (Short Tau Inversion Recovery) sequence,         oriented parallel to the C4/5 through C7/T1 neural foramina as         seen on sagittal images of the localizer sequence. Slices are 3         mm thick, with 0 mm interslice gap, and are prescribed from the         neural foramina posteriorly to the level of the anterior scalene         muscles anteriorly on the affected side(s).     -   3. Sagittal gradient echo T1, spin-echo T1, or fast spin echo         T2-weighted sequence, with slice thickness of 4 mm, interslice         gap of 0 mm, prescribed from the coracoid process on the left to         the coracoid process on the right.     -   4. Axial gradient echo T1, spin-echo T1, or fast spin echo         T2-weighted sequence, with slice thickness of 4 mm, interslice         gap of 0 mm, prescribed from the middle of the C4 body         superiorly to the mid-portion of the aortic arch caudally.

The patient is then removed from the scanner, placed back in the scanner with both arms in hyperabduction and external rotation (approximately 135 degrees of abduction), and a torso PA coil is placed under the patient's back and over the patient's neck and chest to cover the upper chest, neck and supraclavicular fossa region on each side. An intravenous line is placed in the patient's antecubital or hand vein at this point in the study. The intravenous line is connected to a standard MRI power injector. The injector is pre-loaded with one syringe of normal saline, and one syringe containing a mixture of 30 cc of gadolinium contrast material and 30 cc of normal saline. The following sequences are then performed:

-   -   5. 3D localizer sequence, using gradient recalled technique.     -   6. Sagittal gradient echo T1, spin-echo T1, or fast spin echo         T2-weighted sequence, with slice thickness of 4 mm, interslice         gap of 0 mm, prescribed from the coracoid process on the left to         the coracoid process on the right.     -   7. Optional axial gradient echo T1, spin-echo T1, or fast spin         echo T2-weighted sequence, with slice thickness of 4 mm,         interslice gap of 0 mm, prescribed from the middle of the C6         body superiorly to the mid-portion of the aortic arch caudally.     -   8. Sagittal phase contrast angiogram, prescribed to cover the         carotid and vertebral arteries in the neck.     -   9. Gradient recalled “black blood” sequence for timing of         contrast injection. 2 cc of the solution containing 50%         gadolinium contrast material and 50% normal saline is injected         into the pre-existing intravenous line, starting at the same         time as the sequence is initiated, and 30 axial images are         obtained at the level of the carotid bifurcation, as determined         by the preceding phase contrast sequence, at the rate of one         image per second. These images are then evaluated for signal         intensity using the ‘functool’ function of a GE Medical Systems         MRI scanner console (or similar function available on all         commercial scanners). A region of interest is placed over the         carotid artery on these axial images, and the signal intensity         over time is plotted, starting at time=0 seconds. The time from         injection to peak signal intensity is determined and noted.     -   10. Magnetic resonance angiogram, oriented in the coronal plane,         prescribed to cover both carotid and vertebral arteries as         determined by the preceding phase contrast sequence (sequence         8). This sequence serves as a ‘mask’ for the next sequence, to         allow reduction of artifact and reduction of background noise.     -   11. Contrast-enhanced magnetic resonance angiogram, oriented in         the coronal plane, prescribed to cover both carotid and         vertebral arteries as determined by the preceding phase contrast         sequence (sequence 8). This sequence is initiated after the         injection of the remainder of the 50% gadolinium contrast/50%         saline solution pre-loaded into the power injector, utilizing         the delay calculated in sequence 9, plus one second. Thus, the         injection is initiated, the calculated delay is observed, and         the sequence is initiated immediately after the delay elapses.         This sequence produces source images for the magnetic resonance         angiogram.     -   12. If desired, contrast-enhanced magnetic resonance venogram,         oriented in the coronal plane, prescribed to cover both carotid         and vertebral arteries as determined by the preceding phase         contrast sequence. This sequence is an exact duplicate of the         immediately previous sequence, (sequence 11), and is initiated         immediately following the completion thereof. This sequence         produces images of the arteries and veins of the upper chest,         neck and upper extremities, which are source images for any         desired magnetic resonance venogram.     -   13. Single shot fast spin echo sequence, oriented in the coronal         plane, 10 mm slice thickness, single slice. This sequence is         used to determine the presence or absence of fluid or edema in         the soft tissues of the upper chest wall and supraclavicular         fossae.

In patients with prior surgery for decompression of the thoracic outlet, the following sequences are then performed:

-   -   14. Axial gradient echo or fast spin echo T1-weighted sequence,         with chemical fat suppression, slice thickness of 4 mm, and         interslice gap of 0 mm. The slices are prescribed from the         middle of the C6 body superiorly to the mid-portion of the         aortic arch caudally.     -   15. Sagittal gradient echo or fast spin echo T1-weighted         sequence, with chemical fat suppression, slice thickness of 4         mm, and interslice gap of 0 mm. The slices are prescribed from         the midline of the spinal canal to the coracoid process on the         post-surgical side(s).

After the above images have been produced, the following reconstructions and reformations are performed on selected images:

-   -   16. Each image from the oblique coronal STIR sequence is         reviewed for the presence of brachial plexus components on the         affected side(s). All images that contain these brachial plexus         components are loaded into the Interactive Vascular         Imaging (IVI) software program on the GE Medical Systems MRI         scanner console (or similar function available on all commercial         scanners), and the surrounding tissues are electronically         removed in all planes, using the ‘Modify Model-Threshold/VOI’         function, leaving only the brachial plexus components on the         affected side(s). One 3-dimensional model is constructed for         each brachial plexus, including all components of the brachial         plexus from the level of the neural foramina medially through         the level of the retropectoralis space laterally on the affected         side(s). Each 3-dimensional model is then rotated in the         horizontal and vertical planes, using the ‘Display Modes-Set         Batch/Movie Loop’ function. Thus, two models of each brachial         plexus are constructed and saved for review.     -   17. Each image in sequence 10 is digitally subtracted from the         corresponding image in sequence 11, producing a new set of         images which represent source images for the arteriogram. These         images are loaded into the Interactive Vascular Imaging (IVI)         software program on the GE Medical Systems MRI scanner console         (or similar function available on all commercial scanners), and         the common carotid arteries, subclavian arteries, axillary         arteries and brachial arteries on each side are identified. One         projection image is constructed for the entire arterial tree,         using a Maximal Intensity Projection (MIP) technique. The         surrounding soft tissues are then electronically removed in all         planes, using the ‘Modify Model-Threshold/VOI’ function, leaving         only the major arteries on the affected side(s). A separate         3-dimensional model is then created for each arterial tree,         including the common carotid artery, subclavian artery, axillary         artery and brachial artery on. the affected side(s) The         3-dimensional model created on each side is then rotated in the         vertical plane, using the ‘Display Modes-Set Batch/Movie Loop’         function.     -   18. Optionally, each image in sequence 10 is digitally         subtracted from the corresponding image in sequence 12,         producing a new set of images which represent source images for         the venogram. These images are loaded into the Interactive         Vascular Imaging (IVI) software program on the GE Medical         Systems MRI scanner console (or similar function available on         all commercial scanners), and the common carotid arteries,         subclavian arteries, axillary arteries, brachial arteries,         internal jugular veins, subclavian veins, axillary veins and         brachial veins on each side are identified. One projection image         is constructed for the entire arterial and venous tree, using a         Maximal Intensity Projection (MIP) technique. The surrounding         soft tissues are then electronically removed in all planes,         using the ‘Modify Model-Threshold/VOI’ function, leaving only         the major arteries and veins on the affected side (s). A         separate 3-dimensional model is then created for each combined         arterial and venous tree, including the common carotid artery,         subclavian artery, axillary artery, brachial artery, internal         jugular vein, subclavian vein, axillary vein and brachial vein         intact on the affected side(s). The 3-dimensional model created         on each side is then rotated in the vertical plane, using the         ‘Display Modes-Set Batch/Movie Loop’ function.

The complete set of 700-1,000 images is reviewed by a radiologist on a workstation. The anatomic and pathologic points of interest to be reviewed and reported are listed below.

In each case, the skilled radiologist will understand that the inspection will reveal the presence or absence of certain features and be able to identify those features that are associated with TOS. In some instances, as in the evaluation of the scalene muscles and certain other muscles of the right and left thoracic outlet, there appears no formal radiology literature on the appearance of these images, but surgery literature is available describing anatomic and pathologic changes in the areas of concern, and the skilled radiologist will be able to interpret these images on the basis of experience and knowledge of this literature.

Cervical spine disease

-   -   Degenerative disc disease     -   Degenerative joint disease     -   Central canal or neural foraminal stenosis     -   Integrity of spinal cord

Neck soft tissues

-   -   Lymphadenopathy     -   Soft tissue mass or cyst in neck, superior mediastinum, lung         apices or supraclavicular fossae

Brachial plexus and other neural structures

-   -   Branching pattern, caliber and signal intensity of brachial         plexus     -   Nerve root avulsion or pseudomeningocoele     -   Size and symmetry of stellate ganglia

Metrics of cervicothoracic junction

-   -   Superior thoracic aperture: measured from the posterior border         of the superior aspect of the manubrium to the anterior cortex         of the vertebral column, in the horizontal plane, as seen on the         midline sagittal image         -   Measured in both arms neutral and hyperabduction-external             rotation positions     -   First rib angle: measured relative to the horizontal, as seen on         the sagittal image demonstrating the longest segment of first         rib         -   Measured in both arms neutral and hyperabduction-external             rotation positions     -   C7 vertebral anatomy         -   Bony tubercles of body         -   Bony bars, extending to transverse processes and forming             pseudo-transverse foramina         -   Enlarged transverse processes         -   Cervical ribs

Right thoracic outlet

-   -   Scalene muscles         -   Size         -   Origins         -   Insertions         -   Interdigitating muscle bands         -   Scalene minimus muscles         -   Fibrous bands         -   Levator costae muscles         -   Slings     -   Scalene triangle-arms neutral         -   Apex         -   Base     -   Brachial plexus         -   Course relative to scalene muscles, scalene triangle and             anomalies of structures in “Right thoracic outlet, Scalene             muscles” listed above.     -   Other muscles         -   Subclavius             -   Size             -   Subclavius posticus variant         -   Pectoralis minor         -   Axillary arch     -   Anatomic tunnels-hyperabduction external rotation         -   Scalene Triangle         -   Costoclavicular interval         -   Subclavius-Serratus space         -   Retropectoralis space

Left thoracic outlet

-   -   Scalene muscles         -   Size         -   Origins         -   Insertions         -   Interdigitating muscle bands         -   Scalene minimus muscles         -   Fibrous bands         -   Levator costae muscles         -   Slings

Scalene triangle-arms neutral

-   -   Apex     -   Base

Brachial plexus

-   -   Course relative to scalene muscles, scalene triangle and         anomalies of structures in “Right thoracic outlet, Scalene         muscles” listed above.

Other muscles

-   -   Subclavius         -   Size         -   Subclavius posticus variant     -   Pectoralis minor     -   Axillary arch

Anatomic tunnels-hyperabduction external rotation

-   -   Scalene Triangle     -   Costoclavicular interval     -   Subclavius-Serratus space     -   Retropectoralis space

MR Angiogram

-   -   Aortic arch branching pattern     -   Great vessels and other major branches         -   Common carotid arteries         -   Vertebral arteries         -   Internal mammary arteries         -   Subclavian, axillary and brachial arteries as they pass             through anatomic tunnels         -   Dorsal scapular arteries and transverse arteries     -   Evaluate vessels for         -   Extrinsic compression         -   Intrinsic stenosis, or vascular disease         -   Post-stenotic dilatation         -   Anomalous course or vessel

MR Venogram

-   -   Neutral position         -   Subclavian and axillary veins         -   Left brachiocephalic vein             -   Compression in superior mediastinum         -   Internal and external jugular veins, and cephalic veins     -   Hyperabduction external rotation         -   Subclavian and axillary veins         -   Left brachiocephalic vein             -   Compression in superior mediastinum         -   Internal and external jugular veins, and cephalic veins     -   Evaluate vessels for         -   Extrinsic compression         -   Thrombus         -   Slowing of flow             -   Suggested by increased luminal signal intensity     -   Change in caliber between neutral and hyperabduction external         rotation     -   Presence of gadolinium contrast in veins

Lymphatics

-   -   Thoracic duct     -   Supraclavicular lymphatics     -   Edema of supraclavicular fossae or chest wall 

The invention claimed is:
 1. A method to evaluate a human subject for the presence or absence of thoracic outlet syndrome (TOS) which method comprises: a) obtaining a first set of magnetic resonance imaging (MRI) slices in each of three planes, in the absence of contrast agent, with the subject in a supine position with both arms in a neutral position by the side of the body, using a surface coil placed to cover the upper chest and neck, and the supraclavicular fossa region on an affected side(s), wherein the obtaining the first set comprises obtaining a gradient echo T1, spin echo T1, or fast spin echo T2-weighted sequence that comprises sagittal slices that cover the scalene triangle, costoclavicular space, and retropectoralis space on the affected side(s), wherein the obtaining the first set further comprises obtaining a gradient echo T1, spin echo T1, or fast spin echo T2-weighted sequence that comprises axial slices that cover the mid and lower cervical spine and lower neck, and the brachial plexus, supraclavicular space, superior mediastinum and lung apex on the affected side(s), and wherein the obtaining the first set further comprises obtaining a Short Tau Inversion Recovery (STIR) sequence that comprises coronal slices that cover the volume of the brachial plexus on the affected side(s); b) obtaining a second set of MRI slices in one or more planes, in the absence of contrast agent, with the subject in a supine position with both arms placed in abduction and external rotation, using the surface coil placed to cover the upper chest and neck, and the supraclavicular fossa region on the affected side(s), wherein the obtaining the second set comprises obtaining a gradient echo T1, spin echo T1, or fast spin echo T2-weighted sequence that comprises sagittal slices that cover the scalene triangle, costoclavicular space, and retropectoralis space on the affected side(s); followed by administering a diluted contrast agent comprising 50% gadolinium into a vein on a first side of the subject such that the contrast agent enters arteries of the subject; obtaining a contrast-enhanced magnetic resonance angiogram (MRA) and a magnetic resonance venogram (MRV), each of which image, in the subject, the contrast agent delivered by the administering, the MRA comprising coronal slices imaging the subclavian and axillary arteries on both sides of the subject, the MRV comprising coronal slices imaging the subclavian, axillary, and brachiocephalic veins on both sides of the subject; c) composing the slices from the STIR sequence into a composite volume, and editing the composite volume to create a three-dimensional model of the brachial plexus on the affected side(s); d) composing the slices from the MRA into a composite volume, and editing the composite volume to create a three-dimensional model of the arteries on the affected side(s); e) composing the slices from the MRV into a composite volume, and editing the composite volume to create a three-dimensional model of the veins on the affected side(s); f) determining a degree of stenosis, if any, in each of the subclavian and the axillary arteries and each of the subclavian, the axillary, and the brachiocephalic veins on both sides of the subject by assessing vascular contrast enhancement, on the both sides, produced by the contrast agent delivered by the administering of the contrast agent into the vein on the first side; and determining the presence or absence of TOS based on an evaluation of the first and second sets and the three-dimensional models of c) and d).
 2. The method of claim 1, wherein the obtaining the second set further comprises obtaining a gradient echo T1, spin echo T1, or fast spin echo T2-weighted sequence that comprises axial slices that cover the mid and lower cervical spine and lower neck, and the brachial plexus, supraclavicular space, superior mediastinum and lung apex on the affected side(s). 